Everything on this page relates to a 1987 Mazda Capella (aka 626, aka Ford Telstar). It probably
applies to many other vehicles - the parts shop told me they sell the same lifters to Subaru owners -
but treat with due caution.

This page reflects my recent laboriously acquired experience with hydraulic tappets (lifters). If
your engine sounds like a giant knitting machine, workshop manuals are not much help - they typically
say things like "Remove the lifters and check their condition". Check them how? What did they
ought to feel like?
That's why I wrote this page. And, because in all my Googling around, I couldn't find anything
useful on the subject.

How they work, sorta

First, a brief description of how the things are supposed to work. You can skip the next few
paragraphs if you like.

The Mazda has a single overhead cam with twin rockershafts - quite a tidy arrangement. The
lifters sit in cylindrical chambers in the end of the rockers. They're fed with oil via the hollow
rockershaft and through a drilling in the rocker. This drilling feeds the chamber above the lifter;
just before the drilling reaches the chamber it steps down a size to restrict the oil feed. The fine
drilling continues out of the top of the chamber to fresh air, so the chamber stays full of oil but
not under pressure.

Mazda rocker with lifter in place

Rocker with lifter removed.
The start of the oil feed drilling can be seen in the bore for the rockershaft.

Seen from above. The tiny hole for the oil bleed
can just be seen on the flat top of the lifter chamber.

The lifter is hollow, it has a light internal spring to keep it extended, and a little non-return ball
valve in its base to let oil in but not out. When compressed, the lifter will very slowly
leak down - this doesn't happen when the motor is running because each time the valve shuts
and the load comes off the lifter, it can suck in oil through the ball valve to replace the tiny
amount that's leaked out. If the oil supply fails (through blockage) then the lifter will
end up sucking in air instead - and will clatter.

Hydraulic lifter

Showing the hole in the base for the ball valve

How should it feel?

If the lifter is OK, then it should feel 'solid', with no springiness. If it's springy, then
it very likely just has no oil in it - it's full of air instead. I found
most replacement lifters I bought were pre-loaded with oil and 'solid', but a few felt 'springy'.
If you can feel any springiness at all (by hand), the lifter will be noisy if installed in
that condition. That doesn't mean it's a dud, it's just oil-starved.

This one feels 'solid'

And this one's 'springy' - probably full of air

If your lifters are clattering

It doesn't necessarily mean they're duds. It may just mean there's some dirt or sludge
in the oil which is clogging the feed drillings in the rocker. If that's the case, fitting
new lifters is a waste of money, it will silence the noise for all of a quarter mile till
the oil leaks out of them. You need to do things like change the oil, fit a new filter, clean
out the drillings in the rockers, and make sure that any lifters which are full of air are
pre-filled with oil.

To check lifters in situ

To check which lifters are noisy, remove the rocker cover and see which rockers have too
much play. Check each rocker when its valve is fully closed, that is when the cam load is
off it. If you can feel a lot of 'rock', say an eighth of an inch (2 or 3mm), then the lifter
will be noisy. Most likely the rocker has a clogged oil feed and the lifter has filled with air.

An easy way to make sure you're checking each lifter with the valve closed is to check no 1
cylinder's exhaust when no 4 is fully open, and vice versa; and no 2 when no 3 is fully open,
and vice versa. Ditto for the inlet valves (in pairs of course).

You can just see from the angle of the rocker that the third exhaust valve back is fully open...
(the inlet rockershaft on the left has already been removed)

... so we check the second rocker by waggling it. Then turn the motor over a bit
and repeat for the other rockers in turn.
(Where'd the water come from? A torrential rainstorm in the middle of it all)

To fix noisy lifters

First, establish which ones are 'springy' as in the above paragraph. Remove the rocker shafts,
and disassemble.

Pull each noisy lifter out of its rocker. It may be stiff, you may need to grip it tightly with
pliers and turn it round in its bore to free it.
Refill the lifter with oil by submerging it in a tray of oil,
squeezing it (by hand) and prodding the little ball valve with a piece of stiff wire (e.g. a
paper clip) to let the air out, then releasing the pressure so it extends and sucks oil in. It
should now feel absolutely 'solid' when squeezed.

Thoroughly clean the oil feed in the rocker. You'll need a fine piece of wire to poke through from the
outer end - the wire should enter the fine drilling above the lifter chamber and continue all the
way to the rockershaft bore in the middle of the rocker.

Then, push the lifter back into its chamber in the rocker. If you can pre-fill the chamber with
a little oil before fitting the lifter, so much the better.

Next, clean up the engine's oil system as much as possible. That is, change the oil and fit a new oil
filter. If the underside of the cam cover is covered in gritty sludge, clean it (the 12-valve
Mazda has a steel plate inside the cover, held in by screws, which can be removed to make cleaning
easier).

Then, reassemble and reinstall the rocker shafts. This is a bit of a fiddly job, to get all the
rockers and the plastic spacers in the right places and not jamming or binding. I found I had to screw
down the bolts little by little, constantly waggling the rockers and pushing the plastic spacers against
the spacer springs to make sure they weren't stuck.

And that's it, or should be. Do check your workshop manual for the right torque settings, of course.

Rocker shaft, partly reassembled. It pays to keep all the bits in the right order...
(This is, of course, the inlet shaft - it has more rockers on it.)

Does it work?

Well, I had incurably noisy lifters. Over the space of a couple of years, I fitted sixteen new
lifters (in a 12-valve motor!) without any lasting improvement. I had tried changing the oil (but
without cleaning the rockershaft drillings, so it didn't do any good). Eventually I followed the
procedure above - took the rocker gear all apart, carefully cleaned the rocker oil drillings, checked
the lifters, removed the steel plate from the inside of the cam cover and scrubbed and waterblasted it
all clean before reassembling it, changed the oil and fitted a new oil filter. It took all morning,
but that was six months ago and I haven't heard a sound from the valve gear since.

Footnote - Oil Filter

The oil filter seems to be quite critical in all this. My motor is now fairly old, probably a lot of
blow-by past the rings to make sludge, and when cornering hard it seems to get stirred up into the oil.
I let the oil get a bit low and yesterday the motor started clattering like a knitting machine factory.
I changed the oil, did the full lifter clean as above, but I didn't fit a new filter as I didn't have one.
The motor started out quiet but within five miles was clattering as badly as before.

So I bought a new filter and fitted it (as I'd intended to do anyway), I didn't dismantle the rocker shafts
again, just probed with a fine piece of wire through the bleed holes and checked by turning the motor on the
starter, (spark plug leads disconnected), that oil was coming out of all bleed holes. (N.B. Don't let the
engine start up when doing this unless you want oil squirted everywhere, guess how I know). At least four
of the lifters had air in them, by feel. The motor was, naturally, clattery when started up but gradually
got quieter and within ten miles all noise had disappeared. Which is what I hoped might happen.

So, as a first step, I'd say change the oil filter first, before doing any of the stuff up top.
(And, like, new oil is probably indicated). If that doesn't silence the lifters within a few miles, then
you'll have to do the full works above.